BACKGROUND: In postoperative Crohn's disease (POCD), data are lacking on relationships between serum biologic concentrations and treatment outcomes. We assessed if established threshold concentrations of infliximab (IFX), adalimumab (ADA), and ustekinumab (UST) impact outcomes in POCD.

METHODS: Data were extracted from POCD patients with serum biologic concentration measurements using Weill Cornell Medicine biobanks. The primary outcome compared rates of deep remission (achieving both objective [endoscopic or biomarker] and clinical [Harvey-Bradshaw index or Crohn's Disease Patient Reported Outcome-2] remission), using established serum drug level cutoffs of IFX ≥3 µg/mL, ADA ≥7.5 µg/mL, and UST ≥4.5 µg/mL.

RESULTS: In 130 patients, median IFX, ADA, and UST concentrations were 10 (interquartile range [IQR], 2.9-26.9) µg/mL, 10.5 (IQR, 4.9-14.9) µg/mL, and 6.9 (IQR, 5.1-10.2) µg/mL, respectively. In patients with IFX ≥3 µg/mL, higher rates of deep remission (39% vs 0%; P = .02) existed compared with those with IFX <3 µg/mL. Similar differences existed for clinical (44% vs 9%; P = .04) and objective (83% vs 62%; P = .1) remission. In patients with ADA ≥7.5 µg/mL, rates of deep (42% vs 0%; P = .02), clinical (42% vs 0%; P = .02), and objective (88% vs 40%; P = .007) remission were higher than patients with lower concentrations. For UST, rates of deep (28% vs 17%; P = 1.0), clinical (33% vs 33%; P = 1.0), and objective (70% vs 67%; P = 1.0) remission were similar between patients regardless of drug concentration.

CONCLUSIONS: In POCD, established anti-tumor necrosis factor concentrations were associated with improved outcomes. No relationship between UST concentrations and postoperative outcomes existed.